[Electrophysiological study on hemifacial spasm--usefulness in the etiological diagnosis and pathophysiological...

Electrophysiological studies were performed in 30 patients with idiopathic hemifacial spasm (idiopathic HFS), who underwent microvascular decompression with abolishment of spasm, and 10 patients with symptomatic hemifacial spasm (symptomatic HFS) secondary to Bell's palsy. (1) The maximum firing rate of abnormal discharges recorded from the orbicularis oris muscle during spasm in patients with idiopathic and with symptomatic HFS, and that of discharges recorded on the intact side during voluntary contraction in idiopathic HFS patients measured 181 +/- 71 Hz, 68.4 +/- 36.9 Hz, 56.3 +/- 21.8 Hz, respectively. Thus, the maximum firing rate of the discharges during spasm in idiopathic HFS patients was exceedingly higher than that in symptomatic HFS patients. (2) Electroneurography, performed to evaluate quantitatively degeneration of the facial nerve, revealed that the ENoG value (90.2 +/- 16.5%) in idiopathic HFS patients were higher than that (57.6 +/- 26.8%) in symptomatic HFS patients. (3) In blink reflex examined, synkinetic potentials (S1, S2), synchronous to the potentials consisting of the early (R 1) and late component (R 2) in the orbicularis oculi muscle, were recorded from the orbicularis oris muscle on the affected side in all patients with idiopathic and with symptomatic HFS. In sequential recording of blink reflex potentials (R 1, R 2) and synkinetic potentials (S 1, S 2), the recording pattern of synkinetic potentials was divided into variable and constant type. In the variable type, synkinetic potentials appeared unsteadily and the difference in latency between R 1 and S 1 was varied. In the constant type, synkinetic potentials appeared steadily and the difference in latency between the two was not varied.(ABSTRACT TRUNCATED AT 250 WORDS)